The present invention relates to a network system constructed of a narrow-band network such as a TDM (Time Division Multiplex) network and of a broad-band network (integrated network) such as an ATM (asynchronous transfer mode) network, and to communication devices constituting the broad-band network.
In recent years, a technology of an asynchronous transfer mode (ATM) has increasingly advanced and spread. As a relay network of data between terminal devices, there appears an integrated network based on one of technologies using an ATM network, wherein conventional time division multiplex (TDM) lines are relayed to ATM lines. The integrated network, for example, is accommodated a plurality of TDM networks (a plurality of TDM-SWs), The integrated network relays data transmitted between the TDM networks.
In the case of constructing the integrated network, it is desired that a detour function be actualized by the integrated network. The detour function is a function that a transmission route of data is charged another route so as to avoidance of a fault occured in a network and the data is transmitted a destination of the data.
Herein, the detour function is explained. FIGS. 16 and 17 are explanatory diagrams each showing the detour function in the TDM network. As shown in FIG. 16, when the TDM network is normal (no fault), it is assumed that, for example, the data transferred from a terminal device 114 to a terminal device 115 be transferred on a route such as the terminal device 114xe2x86x92a TDM-SW (TDM switch)xe2x86x92a DMIX (multiplexer) 501xe2x86x92a DMIX 502xe2x86x92a TDM-SW 112xe2x86x92a DMIX 502xe2x86x92a DMIX 503xe2x86x92a TDM-SW 113xe2x86x92the terminal device 115.
Herein as shown in FIG. 17, for instance, if a fault occurs in the TDM line (a relay line) for connecting the DMIX 503 to the TDM-SW 113, the data transferred from the terminal device 114 to the terminal device 115 can not be transferred on the route described above. Therefore, the TDM-SW 112 changes the route such as the TDM-SW 112xe2x86x92a public network 116xe2x86x92the TDM-SW 113xe2x86x92the terminal device 115, thus detouring around the line in which the fault occurs.
Incidentally, a plurality of TDM-SWs (e.g., PBXs (Private Branch Exchanges)) constituting the TDM network set a path in a link-by-link manner by terms of a characteristic of the TDM. If the relay line in which a link should be set can not be connected, the TDM-SW accommodating this relay line sets the link in other relay line by executing a detour function.
In contrast with this, as shown in FIG. 18, when the TDM networks are bridged by the ATM network, each of ATM-WAN (Wide Area Network) nodes (hereinafter abbreviated to xe2x80x9cAWNSxe2x80x9d 600-603 constituting the ATM network, is capable of directly setting a VC (Virtual Channel) from a transmitting side AWN to a receiving side AWN.
For example, as shown in FIG. 18, when data communications are carried out between the terminal device 114 and the terminal device 115, the terminal device 114 transmits to the TDM-SW 111 call-out information (such as dial information) etc) containing call-in address information (a destination address). The call-in address information includes an intra TDM network node address number xe2x80x9c730xe2x80x9d for specifying the TDM-SW 113 and an intra TDM-SW 113 terminal device address number xe2x80x9c2000xe2x80x9d for specifying the terminal device 115.
The TDM-SW 111 transmits, to an AWN 601, call setting signaling (a call setting message) containing the call-in address information requesting the terminal device 115 to receive. The AWN 601, when receiving the call setting signaling from the TDM-SW 111, controls a transmission of the call setting signaling in accordance with a procedure of xe2x80x9cSTR-VTOA-LLT-01.12xe2x80x9d based on recommendations of ATM-Forum.
Namely, the AWN 601 detects an intra broad-band network ATM address xe2x80x9cawn3xe2x80x9d corresponding to the call-in address information xe2x80x9c730xe2x80x9d contained in the call setting signaling, and edits a broad-band call setting message. Next, the AWN 601 transmits the broad-band call setting signaling toward the AWN 603 in order to set a narrow-band signaling transmission VC. As a result, the narrow-band signaling transmission VC is directly set between the AWN 601 and the AWN 603.
Incidentally, as shown in FIGS. 19 and 20, a fault or a line busy etc occurs in the TDM line through which the AWN 601 is connected to the TDM-SW 111, the AWN 601 is unable to receive the call setting signaling from the TDM-SW 111. Therefore, the narrow-band signaling transmission VC can not be set between the AWN 601 and the AWN 603. In this case, for example, the TDM-SW 111 makes route such as the public network 116xe2x86x92the TDM-SW 112xe2x86x92the AWN 602xe2x86x92the AWN 603xe2x86x92the TDM-SW 113, whereby the call setting signaling can be received by the TDM-SW 113.
In the conventional ATM network (each of the AWNs 601-603) has not detour function descrived above. Hence, if the transmitting side TDM-SW (which is herein the TDM-SW 111) actualizes the detour function described above, the transmitting side TDM-SW holds all pieces of detour information in the ATM network, and must control the detour (routing) in the ATM network.
On the other hand, in terms of a promotion of utilizing the ATM network as a relay network for bridging the TDM networks, it is desirable that the ATM network be constructed so that the ATM network accommodates the TDM network without changing the configuration of the existing TDM network (a PBX network). That is, if the narrow-band signaling transmission VC ca not be set, the transmitting side AWN (the AWM 601 in FIG.19), it is desirable, actualizes the detour function.
It is a primary object of the present invention, which was devised to overcome the problems described above, to provide a network system and a communication device that are capable of actualizing a detour function without changing a configuration of an existing TDM network.
To accomplish the above object, the present invention adopts the following construction.
According to a first aspect of the present invention, A network system of the present invention comprises a TDM network including a plurality of TDM switches connected to each other via TDM lines and an ATM network including a plurality of communication devices connected via the TDM lines in such a state as to be paired with the TDM switches. Each of the communication devices in this network system comprises a first call setting unit for setting, when receiving a call setting request message from the transmitting side TDM switch, a call between this communication device and a receiving side communication device paired with the receiving side TDM switch indicated by the call setting request message, a specifying unit for specifying, if the first call setting unit is unable to set the call, any one of TDM switches excluding the receiving side TDM switch as a detour TDM switch, a storing unit stored with detour information for setting the call between the detour TDM switch specified by the specifying unit and the receiving side TDM switch, a reading unit for reading the detour information when the specifying unit specifies the detour TDM switch, a second call setting unit for setting a call between the communication device and a detour communication device defined as a communication device paired with the detour TDM switch specified by the specifying unit, and a unit for making, when the second call setting unit sets the call, the detour communication device transmit a call setting request message containing the detour information read by the reading unit to the detour TDM switch. The detour TDM switch sets the call between the detour TDM switch and the receiving side TDM switch on the basis of the detour information contained in the call setting request message received from the detour communication device.
According to the first aspect of the present invention, when each communication device receives the call setting request message from the transmitting side TDM switch, the first call setting unit sets the call between the transmitting side communication device and the receiving side communication device. If the call can not be set, the specifying unit specifies the detour TDM switch, and the second call setting unit sets the call between the transmitting side communication device and the detour communication device. Thereafter, the call setting request containing the detour information is transmitted to the detour TDM switch from the detour communication device, and the detour TDM switch sets the call between the detour TDM switch and the receiving side TDM switch on the basis of the detour information. According to the present invention, the detour function can be actualized in the ATM network, and hence a communication efficiency can be enhanced.
Exemplified as the communication device are a variety of communication devices used as nodes in the ATM network it such as an ATM switch, an ATM-HUB, an ATM router etc.
These together with other objects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.